We learn in the first episode of Mayoi Jiangshi that Araragi time-travels the night of the end of summer break, which is August 20th.
However, in Ougi's conversation with Araragi at the beginning, both are wearing school uniforms and clearly are at school. So the conversation cannot have taken place right before the events of Mayoi Jiangshi, since the "present-day" events of the arc take place during the summer holidays.
Moreover, after the conversation, Araragi says in his narration:
In the end, Ougi just wanted to teach me some trivia that all intersections have a three-second period where all lights are red [. . .] And I'm reminded of that trivia alongside memories of Mayoi Hachikuji. I'm reminded of those words along with a lost young girl. Every traffic light in the way was red. And in the instance she crossed on green, she was run over.
I recall it with the memories of that girl who died over 10 years ago. That summer's epic adventure. Along with that story that started as a petty concept but in the end grew into a giant tale that almost engulfed everything that was real.
(Paragraph breaks are mine.) This is before a break in the story and the subsequent introduction of the events of August 20th.
Here, Araragi cannot only be recalling the story of Hachikuji's death; he must also be recalling his time-travel adventure in this narration of his thoughts. (The appearance of a number of frames associated with events late into Mayoi Jiangshi in this section provides additional support for this.)
The conversation must then take place at some unspecified point after the events of Mayoi Jiangshi. Thus, there is no inconsistency with Kanbaru's introduction of Ougi to Araragi "on a certain day at the end of October" in Owarimonogatari.